France's second largest port, Le Havre, is at the gateway between the North Sea and the Atlantic Ocean. One of France's largest oil refineries is located here. To connect the plant directly with the oil tanks, a new, more efficient pipeline with a length of 1,500m is to be installed. For this purpose, a specialized contractor developed a turnkey solution, to cross two shipping channels at depths of down to 70m with a groundwater pressure of up to 7 bar. Since the geological conditions did not allow the use of HDD technology on the first section, a Herrenknecht AVN Machine, owned by contractor HDI Horizontal Drilling International S.A. was specifically modified to become retractable for the project. At both sides of the ship channel the machine excavated a 200m long casing pipe with an inclination of 12 degrees down to the bedrock at a depth of 35m. Subsequently, the machine was recovered through the installed casing.
The contractor used two HDD Rigs to drill the pilot holes through these pipes and enlarged the boreholes. To get a perfect alignment and centralization at each casing underground extremity, the drills started simultaneously from both sides and met under the basin. In order to avoid port traffic being affected during the subsequent pipe installation, the pipe string was positioned on an 850-meter-long support structure and installed with up to 60 tonnes accurately and on schedule.